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Cryptic translocation t(5;18) in familial mental retardation
A Vogels1, K Devriendt, J R Vermeesch
1Center for Human Genetics, University Hospital Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
Annales De Genetique
|February 13, 2001
Summary
A cryptic translocation t(5;18) was found in a large family, leading to developmental delays and distinct physical features in affected individuals. This genetic abnormality highlights the importance of subtelomeric region analysis in diagnosing complex genetic disorders.
Area of Science:
- Genetics
- Cytogenetics
- Human Genetics
Background:
- Subtelomeric regions are crucial for chromosomal stability and gene regulation.
- Cryptic translocations can be challenging to detect with conventional cytogenetic methods.
- Fluorescence in situ hybridization (FISH) with subtelomeric probes enables detailed analysis of chromosome ends.
Observation:
- A cryptic translocation t(5;18)(qter;qter) was identified in a large family using FISH.
- Affected individuals presented with unbalanced karyotypes, specifically duplication of 5qter and deficiency of 18qter.
- A novel association of clinical features was observed in individuals with this unbalanced translocation.
Findings:
- The unbalanced karyotype resulted in moderate to severe mental retardation, microcephaly, and growth retardation.
- Distinct facial dysmorphism, narrow auditory canals, genital hypoplasia, and behavioral difficulties were noted.
- Some features overlapped with known 18q deletion and 5q trisomy syndromes, suggesting complex genotype-phenotype correlations.
Implications:
- This study describes a previously unrecognized syndrome associated with a specific cryptic translocation.
- The findings underscore the utility of subtelomeric FISH in diagnosing complex genetic disorders.
- Understanding these translocations aids in genetic counseling and potential therapeutic strategies for affected families.